Sheet detector for use with printing press



Oct. 31, 1961 E. D. NASH SHEET DETECTOR FOR USE WITH PRINTING PRESS Filed May 2, 1958 INVENTOR. :32 MER 0/44 5 A445 M Q TTORNEYS V United States Patent 3,006,450 SHEET DETECTOR FOR USE WITH PRINTING PRESS Elmer Dale Nash, Dayton, Ohio, assignor to Harris-Intertype Corporation, Cleveland, Ohio, a corporation of Delaware Filed May 2, 1958, Ser. No. 732,502 13 Claims. (Cl. 192-127) The present invention relates to detectors, particularly sheet material detectors, for detecting whether or not sheet material is present at a predetermined position and for performing a control operation in the absence of the sheet at the position.

One type of detector to which the present invention relates includes a movable conductive member which engages one side of the sheet material being sensed when the latter is at the desired position and which is moved into engagement with a contact member disposed on the other side of the sheet material if the latter is absent from the position at the time of sensing. When the detector is detecting sheets which are successively moved to the position, the movable conductive member is oscillated in relationship to the movement of sheets to the position and is moved toward engagement with the contact member when it is desired to sense the presence or absence of a sheet. If the sheet is present at the desired location, it prevents the contact of the movable conductive member with contact member; if the material is absent, the mov able conductive member engages the contact member to complete a control circuit. If the detector is sensing the presence of a continuous web, or the equivalent, it need only be urged into engagement with one side of the web rather than oscillated.

In the type of detector under consideration, the movable conductive member is normally disposed clear of the path of movement of the sheet and of the plane of the sheet. The only time the movable member is disposed in the plane of the sheet material or the path of movement thereof is when it is moved through the position normally occupied by the sheet material in the absence of the latter at the time of sensing. It can be readily understood that when the material being sensed is a thin sheet, such as a sheet of paper to be fed to a printing press, the additional movement of the finger between its position where it is in engagement with the sheet being sensed and its position where it is in contact with the contact member is very little and that, heretofore, the sheet-engaging portion of the element has, therefore, been substantially the same as the contact-engaging portion.

In operation, the type of detector described has heretofore been subject to malfunctioning since the sheetengaging portion and the contact-engaging portion have, as mentioned above, been substantially the same and when the detector is used to sense the presence or absence of paper, particularly glossy paper, an insulating film tends to build up on the movable conducting member which interferes with the ability thereof to establish a circuit when the movable conductive member engages the contact member.

The principal object of the present invention is to provide a detector of the type referred to having a conductive member which engages a contact member when sheet material is absent from a position between the members and engages one side of the material rather than the contact member when the material is present and which is not subject to malfunctioning due to the build-up of an insulating film picked up from the material being sensed or due to an accumulation of ink and dirt.

Another object of the present invention is to provide a detector of the type referred to having a conductive 3,006,450 Patented Oct. 31, 1961 member which engages a contact member when sheet material is absent from a position between the members and engages one side of the sheet material rather than the contact member when the material is present and in which the conductive member has a contact-engaging portion different from the part thereof that engages the material.

A further object is to provide a detector of the type referred to which is suitable for use with electrically conductive sheet material as Well as with sheet material of an insulating nature and which includes a sensing member having a non-conducting portion adapted to engage the sheet material and a conductive portion adapted to engage the contact member on the other side of the sheet material.

It is a still further object of the present invention to provide a sheet-handling mechanism having in combination therewith a detector for detecting the presence or absence of a sheet at a predetermined position and which includes a movable sensing element oscillatable to and from engagement with either the sheet, if the latter is positioned properly, or with a contact member in the absence of a sheet at the predetermined position, the sensing element including a wheel adapted to ride on the sheet and a conductive part diiferent from the wheel for engaging the contact member.

Further objects and advantages of the present invention will be apparent from the following detailed description of the preferred embodiment thereof made with reference to the accompanying drawings in which:

FIG. 1 is a fragmentary plan view of a portion of a sheet-fed printing press showing the sheet feeder and the cylinder of the press which receives the sheet from the sheet feeder;

FIG. 2 is an enlarged sectional view taken approximately along line 22 of FIG. 1 with parts omitted;

FIG. 3 is a view taken approximately along line 3-3 of FIG. 2; and

FIG. 4 is a circuit diagram schematically showing the manner in which the sheet detector element controls the operation of the press.

While the present invention is susceptible of use in various types of detectors for detecting the presence or absence of material at a predetermined position, it is particularly useful in a sheet feeder for a printing press where the sensing element is periodically rocked to a sensing position in timed relationship to the feeding of the sheets to the press to determine whether or not a sheet is in proper position to be fed. It is particularly advantageous where sheets of conductive material or where sheets of high gloss paper are being handled. In the latter case an insulating film builds up on the portion of the detector which normally engages the sheet for, as mentioned above, the sheet-engaging portion in the type of detector involved in the present application has heretofore been conductive and engageable with a contact member in the absence of a sheet to provide a signal that the sheet is absent.

Referring to the drawings, sheets of paper or other material, designated by the reference numeral 10, are fed to the cylinder 11 of a printing press by a sheet feeder 12. The cylinder 11 may be an impression cylinder of a printing couple or a feed cylinder which subsequently passes sheets to the impression cylinder. In either case, the cylinder carries gripper fingers (not shown). These fingers may be what are commonly termed in the printing art tumbler grippers, in which case they grip a sheet at rest on a feed table 13 and carry it into the press; or, they may be used in combination with conventional feed roll mechanism which drives the sheet to the grippers. The sheet feeder 12, in the illustrated embodiment, is adapted to deliver from a pile of sheets, not shown, sheets of material in underlapped fashion or sheet by sheet with a space between them to a position from which they move onto the cylinder 11; and since the structure of the sheet feeder is conventional, it is not shown or described in detail. The particular manner of delivering sheets from the pile to the machine is immaterial to the invention, and the word stream will be used in the remainder of the specification and claims to depict any suitable method of delivering sheets in succession from a pile of sheets to a feed position from which they move in timed relationship to the operation of the machine.

The sheet feeder 12 may comprise a feed table 13 which terminates adjacent to the cylinder 11, and moving tapes (not shown) which engage the underside of the sheets to be transferred to move the individual sheets successively into engagement with a pair of front stops r guides 15, only one of which appears in the drawing, at the exit end of the table 13 adjacent to the cylinder 11. The front stops or guides 15 stop the individual sheet in proper position and registry for the latter to be fed to the cylinder 11 in timed relationship to the operation of the press and the stops are mounted on a rockshaft 16 supported above and extending transversely of the table 13. The shaft 16 is rockable to move the stops to a position for stopping and registering the sheets 10 and to a clear position to permit feeding of the sheets to the cylinder 11.

An electrical sheet detector is provided to determine whether or not a sheet has been properly delivered against the stops 15 so as to be in position for transfer to the cylinder 11. The sheet detector includes two electrically conductive members which are relatively moved into engagement with each other to complete a control circuit each time a sheet is not in the feed position at a predetermined time.

In the preferred and illustrated embodiment, the sheet detector includes a detector head or first member 20 mounted on a rockshaft 22 and including at detecting finger 23. The detector head 20 is rocked by the rockshaft 22 from an inactive position where the finger 23 is clear of the table and the sheets thereon to a second position where the finger 23 engages a contact member or second member forming a part of the feed table 13, or to a first position wherein the finger 23 engages the sheet 10 supported on the feed table in timed relation to the operation of the press. The movement of the rockshaft 22 is such that the finger 23 is moved toward engagement with the contact member 24 each time a sheet 10 is, if the sheet feeder is operating properly, positioned against the stops 15. If the sheet has been delivered against the stops 15, the presence thereof will prevent the finger 23 from contacting the contact member 24. If, however, the sheet is absent at stops 15 when the finger 23 moves toward the contact member 24, the finger will engage a part of the contact member 24. Preferably, the finger 23 is rocked downwardly into momentary contact with the contact member 24 or the sheet thereon to sense the presence or absence of the sheet and then is rocked upwardly so that it does not interfere with the movement of the sheet from the feed table to the cylinder.

The finger 23 of the detector head 20 is a spring finger and is supported in and extends from a recess 25 at one end of an elongated support member 26 formed of an insulating material and supported by a holder 27 mounted on the rockshaft 22 for rocking movement therewith. The holder 27 and the elongated support member 26 all constitute a part of the detector head 20. The spring finger 23 includes a coiled portion 28 disposed adjacent to the bottom of the recess 25 and an outer straight portion 29 disposed exteriorly of the recess 25 and bent at its outer end to provide an axle portion 30 extending transversely to the straight portion 29 and parallel to the table 13. The coiled portion 28 of the spring finger 23 receives the head of a bolt 32 which fastens the finger 23 to the elongated support member 26. The support member 26 has an axial bore 33 therein which receives the shank of the bolt 32. The end of the support member 26 remote from the spring finger 23 is disposed in a counterbore 34 in the holder 27 and the corresponding end of the bore 33 is counterbored to receive a nut 35 threaded onto the end of the bolt 32. The nut 35 secures the bolt 32 and spring 23 to the elongated support member 26 and also provides means for making an electrical connection to the bolt 32 and the finger 23. The holder 27 is provided with a setscrew 36 for securing the support member 26 in the counterbore 34. The setscrew 36 is received in an axially extending slot 37 in the support member 26 to permit endwise adjustment of the support member and, in turn, of the finger 23.

The holder 27 also has a bore 37 coaxial with the counterbore 34 and extending from the counterbore 34 to the far end of the holder 27. The side walls of the bore 37 are slotted at the far end of the holder and the holder has a bore 40 which receives the rockshaft 22 and which intersects the bore 37. The slotted side walls of the bore 37 provide resilient jaw like portions on the side of the rockshaft 22 remote from the finger 23 which are drawable together by a machine bolt 41 to securely clamp the holder 27 on the rockshaft 22. The machine bolt 41 passes through an opening in one of the jaw-like portions and threads into the other.

The finger 23 of the detector head includes a wheel or first part 42, preferably of an insulating plastic, supported on the axle portion or second part 30 of the finger which may be doubled back as shown to limit the axial movement of the wheel. The wheel 42 engages a sheet 10 if it is registered against the front stops 15 at the time the detector head is rocked toward the table 13. If the sheet 10 is not registered against the front stops 15 and is not disposed in the path of movement of the wheel 42 when the head 20 is rocked toward engagement with the contact member 24, the movement of the rockshaft 22 will carry the wheel 42 through the position normally occupied by the sheet 10 and into a recess 44 in the contact member 24. The width of the recess 44 and the rocking movement of the head 20 are such that when a sheet is absent the axle portion 30 extending from the wheel 42 will engage the part of the feed table adjacent the recess 44.

The contact member 24 engaged by the axle portion 30 is a metallic contact member set in a cutout in the part of the table 13 forming the exit end of the feed table. The conductive contact member 24 and the finger 23 are connected into an electrical control circuit for the sheet feeder and the press so that when the axle portion 30 of the finger 23 engages the contact member 24, a circuit is completed and a control operation is performed, preferably a tripping of the press to slow speed and the throwing off of printing pressure and like devices. in the preferred form of the invention, the contact member 24 is at ground potential, as is the entire press, including the feed table 13 and front stops 15. They are all electrically interconnected.

FIG. 4 is a simplified diagram of a circuit into which the detector 20 is connected. As is shown in FIG. 4, the contact member 24 and the spring finger 23 are connected in series circuit with a resistance across a power supply for supplying the plate-to-cathode potential of an amplifying tube 51. The tube 51 has a control grid 52 which is connected to one end of the resistance 50 and when the finger 23 engages the contact plate 24 current flows through the resistance 50 and biases the tube 51 more positively. The increase in current flow in the tube 51 effects operation of a relay 55 having its relay coil 56 connected into the cathode circuit of the tube 51. The relay 55 has contacts 57 which close upon energization of the relay coil 56 to effect energization of a solenoid 58 for effecting reciprocation of a link '59 connected to the tripping mechanism for the press. Preferably, the magnitude of the resistance 50 is such to limit the current fiow in the series circuit including the finger 23 and the contact member 24 to a magnitude incapable of producing any noticeable sensation of shock to the operator of the press in the event he should accidentally engage the finger 23 while he is grounded.

In operation, the insulating film which normally builds up on a detecting element in the type of sheet feeder dis closed when used to detect paper will build up on the wheel 42 rather than on the part which engages the contact member 24 and, therefore, the contact resistance between the axle portion 30 and the contact member 24 is not increased due to the pickup of this insulating film during the operation of the press and sheet feeder. If the sheets being fed are of insulating material, there is no requirement that the wheel 42 has to be of insulating material. If, however, the material being fed is of a conductive material, the wheel 42 must be an insulator since otherwise the sheet would complete the circuit between the finger 23 and contact member 24 or other parts of the press electrically connected to and at the same potential as the member 24 each time a sheet is fed. The usual type of conductive material fed on such a press is foil having a non-conductive paper or coated backing. When a sheet is against the front stops and the detector moves down into engagement with the sheet, a circuit probably would be completed between the finger 23 and front stops if the wheel 42 was conductive and if the stops 15 and contact member 24 were electrically connected and at the same ground potential. This is, of course, prevented by providing that the Wheel 42 be an insulator.

While the portion of the detector head that engages the sheet is preferably a Wheel, as disclosed, it will be understood by those skilled in the art that a sheet detector will function in accordance with the disclosed invention if a conductive portion thereof different from the sheet-engaging portion engages the contact member 24. \A wheel, however, will easily ride on the sheet in the event that it is still moving when contacted by the wheel. This prevents the sensing element from interfering with the registration of the sheet being sensed.

It can now be seen that the present invention provides a new and improved detector having a conductive sensing element which is moved toward engagement with a contact member to complete a control circuit and in the presence of material being sensed engages one side of the material rather than the contact member and in the absence of the material moves through the position normally occupied by the material into engagement with the contact member, the sensing member having a contact-engaging portion which does not engage the material being sensed when the material is present. Furthermore, the sensing element is suitable for use to sense materials which are either insulators or conductors.

Having thus described my invention, what I claim is:

1. In a mechanism for continuously and successively feeding sheets to a predetermined position, a sensing device for sensing the presence or absence of a sheet at said predetermined position, said sensing device comprising a first member, means movable supporting said first member for movement from an inactive position wherein said first member is disposed to be clear of sheet material in said sheet position to a first position wherein said first member is disposed to engage one side of the sheet material disposed in said sheet position and to a second position beyond said first position from said inactive position in the absence of material at said sheet position, said first member having a first part adapted to engage said sheet material and a second part displaced from said first part to be clear of said sheet material when said first member is in its said first position, said second part comprising an electrical contact portion, a second member having an electrical contact portion, and means supporting said second member in position to be engaged by said contact portion of said second part When said first member is in its said second position.

2. In a mechanism, the combination as defined in claim 1 wherein said first part is a wheel adapted to roll on said material.

3. In a mechanism for continuously and successively feeding sheets to a predetermined position, a sensing device as defined in claim 1 wherein said members are disposed to be on opposite sides of sheet material in said sheet position.

4. In a mechanism for continuously and successively feeding sheets to a predetermined position, the structure as defined in claim 3 wherein said first part is a wheel and said second part is an axle rotatably supporting said wheel.

5. In a mechanism for continuously and successively feeding sheets to a predetermined position, the structure as defined in claim 4 wherein said second member has a recess therein receiving said wheel.

6. In a mechanism for continuously and successively feeding sheets to a predetermined position, a sensing device for sensing the presence or absence of an insulationbacked conductive sheet at said predetermined position and initiating a control operation affecting the sheet feeding mechanism in the absence of a sheet at said position, said sensing device comprising first and second conductive members disposed to be on opposite sides of a sheet in said predetermined position, means supporting said first member for periodic movement from an inactive position wherein said first member is disposed to be clear of a sheet in said predetermined position and said second member toward a first position wherein said first member is disposed to engage a sheet in said predetermined position and toward a second position beyond said first position wherein said first member is disposed to engage said second member in the absence of material in said predetermined position, said second member being electrically connected to and at the same electrical potential as the sheet feeding mechanism, the conductive side of said sheet when in said predetermined position being disposed to be engaged by portions of said sheet feeding mechanism when the first member is in its said first position and said first member having an insulated sheet-engaging portion and a conductive part different from said sheet-engaging portion displaced from said sheet-engaging portion and disposed to be clear of a sheet between said members when said first member is in its said first position, and means supporting said second member in position to be engaged by said conductive part upon movement of said first member to its said second position and circuit means connected to said conductive part and to said second member and completed upon the engagement of said part with said second member to effect said control operation.

7. In a sheet feeding mechanism, the combination as defined in claim 6 wherein the insulated sheet-engaging portion of the first member extends closer to said second member than said conductive part, and wherein clearance of said sheet-engaging portion past said second member is provided to enable physical contact of the conductive part of the first member with the second member upon absence of a sheet from the predetermined position.

8. In a sheet feeding mechanism, the combination as defined in claim 6 wherein the second member and said sheet feeding mechanism are at ground potential.

9. In a mechanism for continuously and successively feeding sheets to a predetermined position, the combination of a sensing device for sensing the presence or absence of an insulation-backed conductive sheet at said predetermined position and initiating a control operation affecting the sheet-feeding mechanism in the absence of such a sheet at said position, said sensing device comprising first and second conductive members disposed on opposite sides of a sheet in said predetermined position, means supporting said first member and operable to periodically oscillate said first member to move the latter toward and from engagement with said second member and into engagement With the conductive side of the sheet being sensed if disposed in position and into engagement with said second member in the absence of a sheet in said position, said second member being electrically connected to and at the same electrical potential as the sheet-feeding mechanism, the conductive side of said sheet being engaged by portions of said sheet-feeding mechanism when the first member is in sheet-engaging position, said first member having an insulated sheet-engaging portion comprising a wheel rotatable on an axis transverse to the sheet-feeding direction and a conductive part di'lferent from said Wheel and engageable with said second member in the absence of a sheet between said members, said conductive part comprising an axle for said wheel and said wheel being insulated to prevent conduction between the periphery of said wheel and said axle, said wheel extending closer to said second member than said axle and clearance of said wheel past said second tember being provided to enable physical contact of said axle with the second member upon absence of a sheet from said predetermined position, and circuit means connected to said axle and to said second member and completed upon the engagement of said axle with said second member to effect the control operation.

10. In a mechanism for continuously and successively feeding sheets to a predetermined position, the combination of a sensing device for sensing the presence or absence of a sheet at said predetermined position and initiating a control operation affecting the sheet feeding mechanism in the absence of such a sheet, said sensing device comprising first and second members disposed to be on opposite sides of a sheet in said predetermined position, means supporting said first member and operable to periodically oscillate said first member to move the latter toward and from engagement with said second member and into engagement with one side of the sheet being sensed if disposed in said position and into engagement with said second member in the absence of a sheet in said position, said first member having a sheet-engaging portion of electrically insulating material adapted to engage a sheet between said members to prevent engagement thereof when said first member is moved toward engagement with said second member and a part different from said sheet-engaging portion which is at all times disposed to be clear of a sheet between said members and which is engageable with said second member in the absence of a sheet between said members upon movement of said first member toward said second member, said second member and at least said part of said first member being electrically conductive, and circuit means connected to said part and to said second member and completed upon the engagement of said part and said second member to effect a control operation.

11. In a mechanism for continuously and successively feeding sheets to a predetermined position, the combination of a sensing device for sensing the presence or absence of a sheet at said predetermined position and initiating a control operation affecting the sheet feeding mechanism in the absence of such a sheet, said sensing device comprising first and second members disposed to be on opposite sides of a sheet in said predetermined position, means supporting said first member and operable to periodically oscillate said first member to move the latter toward and from engagement with said second member and into engagement with one side of a sheet when the latter is disposed in said position and into engagement with said second member in the absence of a sheet in said position, said first member having a sheet-engaging portion of electrically insulating material adapted to engage a sheet disposed between said members to prevent engagement thereof when said first member is oscillated toward said second member and a part different from said sheet-engaging portion which is at all times disposed to be clear of a sheet between said members and which is engageable with said second member in the absence of a sheet between said members, said part of said first member being electrically conductive and said second conductive member having a recess therein which receives said sheetengaging portion when said part is in engagement with said second member, and circuit means connected to said part and said second member and completed upon the engagement of said part and said second member to effect a control operation affecting the operation of said mechanism.

12. in a mechanism for continuously and successively feeding sheets to a predetermined position, the combination comprising a spring finger disposed to be on one side of a sheet in said predetermined position and a contact member disposed to be immediately adjacent the other side of a sheet in said predetermined position, a support member, means pivotally mounting said support member adjacent said predetermined position on said one side for oscillation about an axis and between limits, means connecting said spring finger to said support memher for oscillation thereby into engagement with said contact member in the absence of a sheet in said position, a sheet when in said position preventing engagement of said contact member and said spring finger upon oscillation of the latter, and means supporting said contact member in a position to be engaged by a part on said finger difierent from the part thereof which is adapted to engage a sheet in said predetermined position, said spring finger including an axle portion extending generally parallel to a sheet in said position and a wheel supported on said axle portion for engaging the sheet being sensed, said contact member having a recess therein for receiving said wheel.

13. In a mechanism for continuously and successively feeding sheets to a predetermined position, the combination comprising a spring finger disposed to be on one side of a sheet in said predetermined position and a contact member disposed to be immediately adjacent the other side of a sheet in said predetermined position, a support member, means pivotally mounting said support member adjacent said predetermined position on said one side for oscillation about an axis and between limits, means connecting said spring finger to said support member for oscillation thereby into engagement with said contact member in the absence of a sheet in said position, a sheet when in said position preventing engagement of said contact member and said spring finger upon oscillation of the latter, and means supporting said contact member in a position to be engaged by a part on said finger ditferent from the part thereof which is adapted to engage a sheet in said predetermined position, said spring finger including an axle portion extending generally parallel to a sheet in said position and a wheel supported on said axle portion for engaging the sheet being sensed, said contact member having a recess therein for receiving said wheel and said wheel being formed from a nonconductive material.

References Cited in the file of this patent UNlTED STATES PATENTS 680,695 Comins Aug. 20, 1901 968,063 La Batt Aug. 23, 1910 1,174,989 Jones Mar. 14, 1916 1,468,754 Smith Sept. 25, 1923 

